WASTED TALENT: Pals say it’s now utterly “pointless” trying to stop LIndsay from drinking — even after she stumbled and sloppily fell into a cactus las month in LA (above) and hit yet-another party a few weeks ago in Hollywood. (SPLASH NEWS)

She’s been banned from an entire chain of high-end LA nightclubs, from Madonna’s VIP area at the Meatpacking District’s Boom Boom Room, from Avenue on the far West Side (the latter ban since lifted) and, possibly, from the entire nation of India after making false claims regarding child labor. (They’re still deciding.)

A veteran of three aborted rehab stints, she is now $600,000 in debt, has no roles lined up, spends days sleeping and nights partying. Her favorite pastimes include stalking ex-girlfriend Samantha Ronson, ditching court dates, tweeting the details of familial dysfunction and her permanent state of victimhood, and getting photographed while stumbling out of nightclubs and into cacti and other plant life.

“I’ve made some dreadful mistakes, but learned from them,” she said during an interview in Britain. “That has probably saved my life. Partying so hard simply isn’t worth it.”

That was February. At last weekend’s Coachella music festival in California, “Lindsay appeared wasted all day Friday,” says a source. “She looked a mess. Her hair was lanky, she’s too thin, and her eyes were glazed. She kept losing her temper over the slightest thing.”

The night before, she’d been drinking vodka and smoking cigarettes at Bar 210 in Beverly Hills, where her ex, Ronson, was DJ’ing. “She could hardly walk, but she made it onto the dance floor and positioned herself in front of Sam, who was clearly not interested,” says an eyewitness. “Lindsay was all over the place.”

“She will look you in the eye and say, ‘I’ve only taken cocaine twice and I’m not a big drinker,’ ” says a source close to Lohan’s inner circle. “And even when you say, ‘Come on Lindsay, we know that’s not true,’ she will continue to lie. Or you get accused of negativity. You can’t win; it’s a pointless conversation.”

Just a few years ago, Lohan was an A-list starlet, working with the likes of Tina Fey, Robert Altman, Jane Fonda and Meryl Streep. She was a triple threat, that rare performer who could sing, dance and act. She made the cover of Vanity Fair at age 19. Critic Roger Ebert compared her to a young Jodie Foster; co-star Streep said that Lohan was “in command of the art form.”

She hasn’t had a role since a 2009 ABC Family TV movie called “Labor Pains.” (She has a 10-minute cameo in Robert Rodriguez’s upcoming gore-fest “Machete,” but nothing else on her slate.) The most recent entries on her résumé include designing a line of leggings called 6126, “creating” a self-tanner, Sevin Nyne (she’s being sued for copying the formula), and getting fired as the “artistic director” of the famed fashion house Ungaro after a disastrous collection last fall.

Women’s Wear Daily called it “cheesy and dated . . . an embarrassment.” The Washington Post said that it “lacked finesse, sophistication, technical skill and any evidence of good taste.”

Her former messes-in-arms — Paris Hilton, Nicole Richie, Britney Spears — have all managed, some to better effect than others, to pull themselves together. None of these former friends have much to do with Lohan anymore.

“Paris and Lindsay are frenemies,” says Radar Online senior editor Maxine Page. “They were hanging out at a club last week and left to go to a party in the Hollywood Hills at 4:30 in the morning. But they didn’t walk into the club together. Paris is remarkably smart about how she wants to be perceived.”

Just as few people know Hilton is a chain smoker who tears through two packs a day, few also know that Hilton — who dubbed a then-out-of-control Britney “The Animal” — occasionally parties with Lohan, who is otherwise, and not to her knowledge, persona non grata in Hollywood.

“She still thinks it’s 2006,” says Lainey Liu, who chronicles young Hollywood on her blog, Laineygossip.com, and as a correspondent on Canadian TV’s “etalk.” “What’s really pathetic is that she’ll tweet people like Demi Moore and Sarah Silverman, who will never tweet her back. She’s in denial.”

Lohan’s alternate reality is aided and abetted by her staff and hangers-on, who do not challenge her bad behavior and who routinely rectify her wrongdoings. After a recent photo shoot, for example, Lohan pilfered the designer clothes that had been loaned, then denied knowing what happened to them.

“The clothes kept disappearing, and we’d ask Lindsay where they were,” says someone involved in the shoot. “She’d just shrug and claim to know nothing about it.” Eventually, someone snuck into her hotel room and retrieved the garments, and nothing more was said.

Lohan’s astounding ability to ignore reality is a trait she shares with her equally, willfully oblivious stage mother, Dina, who often refers to the 23-year-old Lindsay as “this child.”

On Friday, just two days after Lindsay blew off her deposition in a civil suit brought against her by three young men who were in an SUV she drunkenly hijacked in 2007 — she went shopping instead — Dina told People magazine that Lindsay is “absolutely, 100 percent” a good influence on her other daughter, 16-year-old Ali. (Ali is currently living with Lindsay in her rented penthouse apartment on Sunset Boulevard.)

As for Lindsay’s $600,000 credit-card debt, Dina claims it’s non-existent: “Yes, Lindsay will spend money, but she has people that run what she does,” Dina told Radar Online. “We kind of cleaned house . . . And in the interim, you know, a bill may be a little late or not, you know, but that’s pretty normal.”

And on the subject of her daughter’s substance-abuse problems, and the public pronouncements of her ex-husband, Michael, that their daughter needs help, Dina said, “Lindsay is in good hands. Everything is fine. He’s trashing a child he doesn’t even see.”

Last week, Michael Lohan publicly crashed Lindsay’s apartment and once again proclaimed his daughter a mess. “Lindsay has to get off the prescription meds, she’s gotta get blockers and she’s gotta get therapy,” he said.

Twitter, in fact, is something of an addiction for Lindsay and another example of her need to rewrite her own reality. She usually posts most frequently at around 2 a.m., and then erases most of those tweets the next afternoon.

“I call it crank-tweeting,” says Liu. “I would suspect that the reason she does that is she’s out of her mind on something. I’ll wake up and screen-cap them, because once Lindsay wakes up and realizes what she did, she deletes them all. She’s famous for it.”

Last October, she tweeted Ronson in a rage, then deleted her ramblings the next day. They read, as it were, in part: “every1 hears anything & everything about our life neway*y not give them the truth? Ur friends r happy, every1 u abide by when give in more & more to their childish, superficial anticsa U TAUGHT me about our “friends” in LA, them coming b/t us, *them being PART OF our “1 on 1″ relationship. I took the biggest chance of my life w/ u & u’ve done nothing but break my heart.”

“It becomes funny,” says Liu of Lohan’s tweets. She adds that the actress “can still sink lower. She could do ‘Dancing with the Stars.’ Or her own reality show.”

“I think, in the back of her mind, she is clinging to a real prospect,” says E! Online columnist Ted Casablanca, “that if she got her act together and really did rehab, of course she could have a great career. Like, ‘One day, when I get tired of designing leggings and pretending to drink water at clubs, it’ll be there.’ I don’t know, will it?”

Liu says she recently spoke with a top agent at CAA who asserts that there’s “no f- – -ing way” Lohan has a shot because, unlike a Robert Downey Jr. or a Kiefer Sutherland or a Charlie Sheen, there is no work ethic. All three of those stars are proven money-makers. Even more inequitably, all three have aged well. “That’s what’s unfair,” says Liu. “A woman cannot get old and cannot lose her looks. Robert Downey Jr. became more handsome as he got older.”

Casablanca thinks Lohan could conceivably make a comeback if she quit “having bitch-fights with Samantha Ronson” and sought actual help. “She’s still trying to make it with her disease running rampant,” he says. “But the self-tanner was the last straw. She’s turning herself into Snooki.”